Watching her son take his first step was the best Christmas present Rachael Bartle could have wished for.

Cameron Bartle defied the odds to take those steps - and continues to do so as he runs around the house bursting with energy.

The Hawke's Bay toddler was born with hypoplastic right heart syndrome, which means the right side of his heart is underdeveloped, leaving the left side to do all the work in keeping him alive.

While quite a common condition, Cameron's case is rare because his heart turned 180 degrees before he was born. Essentially, it is now back to front.

A sonographer first noted that something "didn't quite look right" when Mrs Bartle had her 19-week scan. She and husband Nick were given several options, but knew they had to give their son every chance they could.

They travelled to Auckland for a caesarean section, not knowing if they would be bringing home an empty car seat. Cameron was born on August 22, 2012. Twelve hours later, he suffered heart failure.

Doctors discovered he had further complications and, at just five days old, Cameron underwent surgery. His heart needed to be "replumbed" to ensure his survival, Mrs Bartle said.

His chest was kept open for two days to allow swelling to go down before he was stitched back up.

It was a surreal time for the Bartles, who juggled shifts at the hospital with caring for their elder son Cory, who was then almost 2.

After eight weeks of "hell on feet", the family returned home to Clive. There were moments when they did not think Cameron would make it through the night. But he did.

"He's the most determined little kid," Mrs Bartle said.

Three months later, he went through his second surgery because he had outgrown his shunt. The family just wanted to wrap Cameron in cottonwool as they settled back into home life. With a such a compromised immune system, a bout of chickenpox could kill him. But Cameron kept battling and, just days before Christmas, took his first steps, aged 17 months. "I didn't think he was ever going to walk," Mrs Bartle said.

He will have his third open heart operation nearer to his third birthday. After that he should have as much chance of surviving as other children.

There will be regular hospital appointments to check blood flow through his arteries, and pressures in his heart. He will probably need a heart transplant later in life.

As medical technology advances, Mrs Bartle believes there's hope for her son. She vows never to take life for granted and is grateful for the little things, like watching her boys chase each other around the house.